Several different kinds of elevating platforms, together with their associated support members, are known to the art. The design of the support member depends, to a large extent, on the kind of tailgate elevator for which it is intended, and to the rocker or pivot arrangement used in each individual case.
In many cases it is difficult to provide a simple and reliable mounting device for connecting the support member to the tailgate elevator and the elevating platform. For example, the support member must be capable of taking up the high loads and stresses to which the platform is subjected, and to transfer these loads and stresses to the tailgate elevator while, at the same time, enabling the elevating platform to be swung readily in the vertical plane. In many cases, it must also be possible to raise the platform readily to a vertical position, even when the platform is located in its lower position. Otherwise, when occupying its lower position the platform may prevent the truck from being reversed closely into a loading bridge. It is sometimes necessary to bring the truck as close as possible to the loading bridge, especially when loading is to be carried out under cover with respect to weather conditions.
In certain cases, elevating platforms of the kind mentioned are constructed from extruded sections. In cases such as these, it is particularly difficult to provide a simple and reliable means of mounting or attachment with respect to the elevating platform, among other things because it must be possible to vary the dimensions of the support member and pivot shaft, for example in dependence upon the number of sections in the complete platform.
U.S. Pat. No. 2,348,993 (Novotney) describes an elevating gate whose support members take the shape of brackets secured to a transverse tie rod. The gate which is lifted to its upper position by means of a hoist rests on the bracket members and is pivotable relative thereto about a further shaft engaged by outer support arms which have a bend at their outer ends.
U.S. Pat. No. 2,525,424 (Novotney) describes a development of this arrangement in which the hoist is replaced by a central frame supporting a hydraulic cylinder and piston assembly. Further, there is added a gate counterbalancing mechanism including torsion springs between said frame and gate.
None of these prior documents presents a solution to the above problems, especially not if the elevating platform or gate comprises extruded sections.